A standard printed-circuit board is formed of a rigid phenolic or epoxy core plate to each of whose faces is laminated a copper foil. Such workpieces are made as described in WO 92/18,334 in a mass-production operation by forming in a lay-up station a stack or book comprised of a bottom relatively thick stainless-steel carrier plate atop which is formed a sandwich of a lower copper foil, a plastic core plate, and an upper copper foil, and a stainless-steel press plate is set atop this sandwich. Further such sandwiches and press plates are stacked atop this sandwich to form the pressable book that is then transported to a plate press where the entire stack is subjected to heat and pressure to polymerize the plastic and thereby bond the foils to the respective faces of the respective core plates. After the pressing operation the carrier plate and press plates are separated from the finished workpieces and are recycled to the lay-up station.
The finished workpieces are etched to form extremely narrow, e.g. 0.003 in wide, circuit paths so the finished workpieces must be produced to very high tolerances with no significant surface defects. Thus it is critical to keep the various elements that are used in the production free of any dust or the like that could form surface defects and make the workpieces unusable.
In the above-cited European patent publication two separate clean rooms are used, one holding the copper foil-sheets and the other the plastic prepreg plates. In one of the clean rooms there is a lay-up station where a foil is laid atop a press plate, then this subassembly is transported through a window between the rooms to the second clean room where the prepreg sheet is set atop it, and then this assembly is transported to a stacking station where the book is formed.
Such a system is fairly complex and takes up a great deal or space.